It Was Discovered That a Larger Proportion of Children Who

Multiple Choice

It was discovered that a larger proportion of children who slept with nightlights later developed nearsightedness, compared to children who did not sleep with nightlights. The headlines read, "Leaving a light on for you children causes nearsightedness!" Later it was pointed out that nearsighted people have more trouble seeing in the dark and are more likely to leave lights on at night for their kids. And those same nearsighted parents are likely to have nearsighted kids. This is an example of

A) a placebo.
B) bias.
C) a randomized block design.
D) a control group.
E) a lurking variable.